When I was a kid, people would often ask me whom I wanted to be when I grew up. I always answered that I didn't know until one day my aunt offered me a picture book about the Pharos of Alexandria. The cover showed a bearded man prodding on two gray mules laden with wood up the spiral ramp inside the huge tower of the lighthouse. The man had to maintain a fire on its upper platform to guide the ships at night. Next time they asked me whom I wanted to be when I grew up, I said that I wanted to work on a lighthouse.